As motor vehicles characterized by their utility become a mainstream choice, consumers demand certain luxuries primarily associated with passenger cars, either due to their inherent design and/or size. One of the features desired by consumers is the automated movement of such items as sliding doors and lift gates. While features offering automated motion are available, the designs for mechanisms used to accommodate manual overrides are lacking in capability and functionality. Further, the systems consume space within the motor vehicle that makes the interior less efficient and aesthetically less appealing.
Continued demand for enhanced passenger convenience and comfort has caused automobile manufacturers to expand power assist functions in most vehicle systems involving movable panels. In most cases, the power assist is implemented via an electric motor and geared transmission mechanically coupled with an associated movable panel whereby the vehicle operator can control the system by simply actuating a control switch.
In addition to more traditional truck-type movable panels, motor vehicles of the hatchback and van configuration typically include an access opening at the rear of the vehicle body and a lift gate selectively opening and closing the access opening. The lift gate is typically manually operated and specifically requires manual effort to move the gate between open and closed positions. Various attempts have been made to provide power actuation for the lift gate but none of the prior art power actuation systems have realized any significant degree of commercial success since they have either been unduly complicated, relatively expensive, or maintenance prone.
It is generally known to provide a power drive system for driving a movable panel such as a sliding door in movement between an open position and a closed position, where the driving arrangement accommodates shifting between manual operation and positively driven powered operation of the panel at any position along its path of movement while providing a control responsive to an overload to stop panel movement in the event an object is trapped by the closing panel. These types of power drive systems are especially well adapted for use in operating the sliding door of a van-type vehicle. Typically, a power drive system is capable of driving an output member coupled to the door to drive the door in either direction over a relatively long working stroke. The coupling between the output member and the door can take the form of a positive mechanical interconnection between the motor and the door operable in either direction of movement as required. Additional problems may be presented where the power drive system is to power the sliding door of a van-type vehicle over and above the forgoing considerations applicable to sliding doors in general.
The power drive system of a sliding door in a van-type vehicle application is conventionally mounted on either longitudinally extending side of the van and the system may be operated by control switches accessible from the driver's seat. However, there are many occasions where the driver may desire to open or close the door manually, such as when the driver is outside the van loading or unloading articles through the sliding door and the controls are out of reach. A positively mechanically linked connection between the door and power source will interfere with manual operation of the door and may disturb a relationship between the door and drive relied on by the control system to sense the position of the door along its path of travel.
Translation of a vehicle panel typically requires an efficient set of machine elements and clutches to allow the panel to overhaul the system. Yet the driving system must drive efficiently and not offer a significant resistance when being overhauled. A soft coupling may be employed to assure system loads remain in the range of acceptable machine element loads. A ball nut is a highly efficient machine element when used with a ball screw. However, the ball screw is rigid and expensive when used in applications requiring significant travel, while generally being incapable of accommodating movement along a path that is not linear.